Electric motor.



W. SPARKS.

ELECTRIC MOTOR. APPLICATION FILED SEPT-11,1914.

1,239,056. Patented Sept. 4, 1917.

UNITED STATES PATENT OFFICE.

WILLIAM SPARKS, OF JACKSON, MICHIGAN, ASSIGNOR TO THE SPARKS-WITHINGTON COMPANY, A CORPORATION OF OHIO.

ELECTRIC MOTOR.

Specification of Letters Patent.

Patented Sept. 4, 1917.

Application filed September 11, 1914. Serial No. 861,220.

This iny'ention relates to certain improvements in electrically operated horns, involving the use of a vibratory diaphragm and a motor driven actuator therefor, and refers more particularly to the electrical distributing system of the motor.

A particular feature of this type of horn is that the commutator brushes are held in' contactwith the commutator by coil springs which heretofore have formed'parts of the electrical connections between the brushes and field windings of the motor. 1

These springs are usually made of tempered steel, such as piano wire, and when used as current conductors are'liable to lose a greater or less degree of resiliency by reason of the heat developed therein after a short period of use, thereby reducing the efliciency of the motor.

The main object, therefore, is to maintain a higher efliciency of the motor than has heretofore been possible by conducting the current from the brushes to the terminal ends of the field winding around the springs through the medium of separate conductors of less electrical resistance than that of the springs.

Other objects and uses will be brought out in the following description.

In the drawings,.Figure 1 is a longitudinal sectional view of the motor showing the means for conducting the current around the brush-actuating springs, and Figs. 2

and 3 are perspective views one of the brush-holders and one of'the conductors therefor. g 1

The illustrated portion of the horn comprises an internally threaded ring 3-, the latter being screwed upon the externally threaded end of the cylindrical motor case -4, andis held in its adjusted' position by a lock nut --5-- also engaging the threaded end of the case -4 and abutting against the outer face of the ring 3' which is con'cavo-convex and arranged with its conample space for the vibration of a dia-- phragm and a rotary actuator 6.

The motor case contains the usual polepieces and field windings for cooperation with a revolving armature 7, having the ends of its shaft journaled in suitable bearings 8- and -9 in the opposite ends of the motor case. The motor may be inclosed byacylindrical dust protective shield13.

In Fig. 1 is shown a pair of diametrically opposite commutator brushes 15 as slidably mounted in sheet metal guides or boxes 16 which together with the terminal ends 17 of the field windings of the motor are secured to the adjacent sides of the motor case -t by screws 18 and serve to receive and retain a pair of coil springs 19, for yieldingly holding said brushes in contact with the commutator.

These springs are usually made of tempered wire, such as piano wire, and if used as conductors for the current are more or less liable to deterioration by overheating which would of course reduce the efficiency of the motor and in order to overcome this liability, I have provided extra conductors 20 of less electrical resistance than that of the springs and extended along the outside thereof with one end in sliding electrical contact with their respective brushes at the inner ends of-the springs and their outer ends in electrical connectionwith the adjacent terminals of the field windings of the motor so as to pass the current around the springs.

As shown, each of the conductors 20 is provided with an enlarged fiat head or base 2-1 and a spring arm '-22 of reduced width, the fiat base 21 being ofl'set at an angle to the spring arm 22 and interposed between the outer end of its coil spring 19 and adjacent end of the brushholder 16 while the spring arm -22 projects through and is guided in a lengthwise slot 23 in one side of the brushholder, and is spring-pressed into contact with the corresponding side of the brush thus completing the circuit around and independently of the coil spring.

One of the terminals of each field winding a threaded aperture in the adjacent end of the brush-holder to firmly hold the latter in operative position.

The outer end of the motor case 4 is partially closed by a cross bar 25 in connection with which the end thrust bearing for the motor shaft is formed.

Although I have shown and described one specific construction and relative arrangement of the parts, I do not desire to limit myself to the same, as changes may be made in the details of both construction and arrangement without departing from the spirit of this invention as set forth in the appended claims.

' What I claim is:

1. In a motor, a tubular brush-holder, a brush slidable within and substantially fitting the holder, a spring within the holder at the rear of the brush normally tending to eject the brush from the holder, and a spring finger having a portion positioned between the rear of the holder and said spring and another portion extending outside the holder and having an end part in contact with the brush in front of the spring for conveying current around the spring,

2. In a motor, a frame, a tubular brushholder secured to the frame, said holder having a longitudinal slot along one side, a brush slidable within and substantially fitting the holder, a spring at the rear of the brush and normally tending to eject the brush from the holder, and a spring finger having a portion within the holder at the rear of the spring and another portion extending through said slot and provided with an end part in contact with the brush in 'ront of the spring to convey current around the spring.

3. In a motor, a frame, a bolt engaged with the frame, a tubular brush-holder having one end adapted for engagement with said bolt, said tubular holder provided with a longitudinal slot extending along one side of the holder, a brush slidable within and substantially fitting the holder, a spring between the rear end of the holder and the brush and normally tending to eject the brush from the holder, and a conductor having a portion positioned within the holder and between the spring and said bolt and another portion extending through said slot and provided with an end part in contact with the brush for conveying current around the spring.

In witness whereof I have hereunto set my hand this 31st day of August, 1914.

. WILLIAM SPARKS.

Witnesses:

LILLIAN WUNDERLICH, W. B. PATCH. 

